Nowadays, various kinds of roof panels removably attached to a ceiling and the like of vehicles have been proposed. There are two kinds of such roof panels; one is swingable or slidable between its closed position closing an opening of the ceiling and its open position opening the opening, and the other is removed or detached from the ceiling in order to open the opening and then stored in a trunk lid (for example, see U.S. Pat. No. 5,031,949).